Examples of labeling machines to which this invention is applicable are those described in U.S. Pat. Nos. 3,765,991; 4,108,709; 4,108,710; 4,181,155; 4,500,386 and 4,704,173. In such machines the label material is supplied in the form of a roll; the label material or web is removed continuously from the roll of label material by a label feed, including a drive roller which contacts the web (bearing against a back-up roller); and the speed of the drive roller determines the speed at which the label web is supplied to the machine. The continuously moving web contacts a cutter head or roller which brings the label between a cutter blade on the cutter head and a stationary blade and severs the label. A label is severed when the cutter blade on a cutter head contacts the stationary blade. The severed label is supplied to the vacuum drum which transports the label on its surface, rotating it past a glue applicator which applies glue to the leading or forward end and to the trailing or rearward end of the label. The label is released at a label release station where it contacts a container which is caused to spin, thereby wrapping the label about it. The trailing end of the label may be lapped over the leading end and secured thereto by glue or, in the case of what is called a spot label which does not extend around the entire circumference of the container, both the leading end and the trailing end of the label are secured to the container by means of glue. Other means than glue may be used for adhering the label to the container, for example, the use of a solvent which when applied to the label forms an adhesive in situ.
There are a number of problems associated with prior art labeling machines. Prior art machines do not accurately coordinate the vacuum drum, cutter drum and web label speeds during the label cutting and label transfer processes. In particular, prior art machines fail to optimally coordinate the speed of the cutter drum with the cutting head during the label cutting process. Also, prior art machines fail to optimally coordinate the speed of the cutter drum with the vacuum drum during the label transfer process.
These problems have a number of consequences. If the cutter head contacts the web at an inappropriate speed, the label may be stretched, which causes it to be displaced. Consequently, the label is misapplied to the container. An inappropriate cutter head speed produces a sliding action between the knife and the label immediately before the label is cut. This sliding action dulls the knife of the cutter head.
Similar problems may arise when transferring a severed label from the cutting drum to the vacuum drum. In particular, if the cutting drum and vacuum drum are at different speeds during the transfer of a label, a nonoptimal transfer may occur.